Agricultural irrigation systems have been used for centuries to apply water to agricultural crops. The first type of irrigation systems were flood irrigation systems in which trenches formed in the soil directed water via gravitational force to an agricultural site. For example, water can be diverted from a river by a gated trench to an agricultural site at a lower elevation. These type of irrigation systems are still in use today in certain areas where water sources and the topography allow, e.g., certain areas of the western U.S.A. and Australia.
Other more mechanized types of irrigation systems are also used. For example, center pivot irrigation systems of the high pressure or low pressure type receive water from an electric powered water pump. The water typically is pumped from a well, river or irrigation pond. Intermittently spaced towers carrying a supply pipe are driven by electric motors or water driven turbines.
Other types of irrigation systems such as “travelers” are also used. In a traveler system, a flexible hose is coupled with a standpipe in a field supplied by a water pump, and a cable is drawn across the field. The water passes through a water driven turbine prior to exiting from a pivoting gun, and the water turbine reels up the cable on a spool, causing the traveler to move across the field dragging the hose behind.
With a center pivot or traveler irrigation system as described above, an appreciable amount of the water is lost through evaporation as the water travels through the air, and through run-off after the water falls to the ground. To reduce evaporation, such irrigation systems may be operated at night. However, depending upon the amount of acreage to irrigate, it may be necessary to operate the irrigation system around the clock, 7 days a week.
Another more recent type of irrigation is drip irrigation, in which water flows at a low pressure (e.g., typically 5 to 15 psi) through a flattened tube and is discharged through openings in the tube in close proximity to the plants. The water exits at a low pressure from the flattened tube, and is thus also referred to as a “drip tape.” A supply header receives water from a water pump and a plurality of the drip tapes are coupled with the supply header in a network of drip tapes corresponding to the particular shape of the field.
A drip irrigation system as described above has the advantages of directly delivering water and nutrients to an area in close proximity to the plants which maximizes plant growth and production, while limiting problems associated with other types of irrigation systems, such as erosion, disease, weed growth, soil saturation, energy costs and water conservation.
It is also known to provide sheet mulch over the soil in the production of fruit and vegetable crops for weed control, plant growth enhancement via solarization (warming) of the soil, extension of the growing season allowing for double and triple crops, reduction of pest infestation, efficient fumigation, moisture retention, improved irrigation efficiency, reduction in labor needed for crop production, increased crop yield, enhanced crop quality, prevention of soil erosion, prevention of nutrient leaching and reduction in crop rot by minimizing contact with soil.
Sheet mulch may be permeable such as a woven mesh, or non-permeable such as non-perforated plastic sheeting. The plastic sheeting may be of different colors such as black to increase the soil temperature, white to reflect light, or red which has been shown to speed plant growth and increase yields. Additionally, the plastic sheeting may be non-biodegradable and removed after the growing season, or biodegradable and left to rot and enrich the soil. For example, certain types of polymeric and polyester plastics are biodegradable.
It is also known to use a drip irrigation system with sheet mulch. The drip tape can be laid on top of the seed bed and the sheet mulch applied over the drip tape. Alternatively, the drip tape can be bonded to the sheet mulch and laid over the seed bed as an integral assembly which saves time. The sheet mulch can further carry a seed tape or individual seeds, further saving time during planting.
Even with an integrated sheet mulch assembly as described above including drip tape and a seed tape, the sheet mulch carries the seeds and the drip tape is spaced laterally apart from the seeds. The water therefore must saturate the soil to an extent that the soil at the seed tape which is laterally spaced from the drip tape becomes moist. Prior to the seed germinating, the seeds are positioned at approximately the same level as the laterally spaced drip tape, and excess water may need to be applied to saturate the soil for proper germination. Even after the seed germinates and the roots grow, the water still must travel laterally for watering of the plant.
What is needed in the art is a sheet mulch assembly which is easy to install, provides proper seed spacing, and accurate application of water and nutrients without overwatering the area under the sheet mulch.